


Virulent Hypothesis

by HardTack (volatileSoloist)



Category: Apex Legends (Video Games)
Genre: Aphrodisiacs, But not in the way you're thinking, Caustic-typical levels of violence, Drugged Sex, Fingering, Genital Torture, Mentions of Blood, Other, Revenge Sex, Unsafe Sex, intersex bloodhound, this is the bad place
Language: English
Status: Completed
Published: 2019-03-28
Updated: 2019-03-28
Packaged: 2019-12-25 17:17:41
Rating: Explicit
Warnings: Graphic Depictions Of Violence, Major Character Death, Rape/Non-Con
Chapters: 1
Words: 4,213
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18265868
Author URL: https://archiveofourown.org/users/volatileSoloist/pseuds/HardTack
Summary: An AU of luckbuster's ficCo-dependent Variable, where Caustic catches up to them and sees his experiment through. Yeah, you know how luckbuster's fic was actually kind of fluffy? This one is not. At all. "Dead dove, do not eat"-style. So go read theirs if you want some lighter material (although you should probably read theirs first before reading this one anyway. do it, it's super good)Disclaimer: Yes, I did get permission to write a spinoff of their story. No, I do not condone Caustic's behavior.





	Virulent Hypothesis

“I’d rather not chase you down,” Caustic called out into the yellow fumes, “You’ll be too tired for me to see the effects of my new toxins.” When there was no response but fading footsteps in the sand, he lowered his shotgun and peered through the fog. It was imperative he find out which direction they went.

“Don’t toy with your targets.” Bangalore reproached, standing a bit behind him and out of reach of the coils of gas.

Caustic simply shrugged before turning around and tapping his forehead. “It’s all a simple mind game, Bangalore, one I imagine they’re fools enough to fall for.” With that, he moved quickly to the other door and to the edge of the platform. He pulled out his skillfully-made dart rifle and took aim at the fleeing figures.

The first few missed their marks, and Caustic cursed before balancing the gun more carefully. Tink! Tink! A couple more darts flew wide, but finally, finally, one connected with a member of the enemy squad, and Caustic grinned, priding himself on his aim.

He would’ve liked to have a larger sample size for the first test, but by now, their enemies were too far away for him to hit, and he was out of darts, besides. He holstered the rifle and stared out into the mess of nearly identical buildings, trying to best determine which way his prey had gone.

“Looks like you lost ‘em,” sighed Bangalore, her fake pity not lost on Caustic.

Rolling his eyes, he countered, “I don’t give up that easily. Who ever learned anything new by not making consistent efforts?” He stood from where he was crouched before gesturing in the direction their targets had been running. “Searching in this area will prove beneficial.”

“We’re supposed to meet Wraith on the other side,” the soldier pointed out, “it doesn’t make sense to—get down!”

At her warning, Caustic dropped low, and the first round of bullets that had been aimed at him passed overhead. He took a moment to glare at Bangalore. “If you hadn’t wasted time arguing with me, we wouldn’t have been spotted. Probability dictates that it’s a squad of three. I’d rather take a chance at an even match with the squad I hit.”

“Are you kidding me?” Bangalore hissed, before ducking down to avoid being shot. She looked like she might argue more, but then, sighing and shaking her head, she said, “You know what, civvie? You wanna go out there and get blindsided, good for you. I’m meeting up with Wraith.”

“I’d hope meeting up with your girlfriend would be productive, but I know better,” Caustic scoffed, and Bangalore flipped him off before firing a round of smoke grenades to cover their respective exits.

Not one to waste time, Caustic vaulted down to the ground-level, landed with a heavy thud, and immediately took off in his pursuit. He wasn’t worried about being spotted yet, so he didn’t bother making efforts to conceal his movements. Odds were that the team he’d marked had wanted to put as much distance between their squad and his. _But,_ he reminded himself, _if the drug has worked correctly, then that teammate will be drastically slowing them down._ With that in mind, he reduced his speed, and began looking more methodically to see if he could spot any tracks.

His first clue was when he found one of the darts he’d fired, because it meant that he’d been aiming in that direction. He debated whether or not to hold onto it, and then decided against it, tossing it aside and continuing to prowl.

Not long after, he got lucky and noticed a spot in the soil that looked like drag-marks. So, clearly his target had been affected after all. Caustic dug out his notebook and noted the approximate time and distance it had been before the first stage of the toxin had begun to take hold of the victim’s nervous system.

He remembered designing that feature; initially, he’d been interested in using it to make it easier to deal with his test subjects, as he was certain they would struggle. Then, he’d realized that would work in more ways than one; if the specimen were trapped in their own body, with no way to deal with the building heat in their system, how long would it take before they started begging for relief? He was dying to know.

From there, all he had to do was follow the tracks in the sand. They grew deeper, with staggered footsteps peppered around as though whoever had been trying to carry them was having trouble. He supposed that ruled out Lifeline as the recipient of the dart. What a shame. Her doctor’s perspective on all of this would’ve been ironic.

Finally, he heard what he thought were voices on the wind, and he crouched around a corner before peeking his head out. From this distance, he was able to recognize the voice; how could he not, with how much it annoyed him? From what he could tell, Mirage was standing somewhere close by, and very likely keeping guard, which meant...

Had his dart hit, of all people, _Bloodhound_? Now that was _interesting_.

Bloodhound, despite all their popularity as a fan favorite and multi-game winner, had remained an enigma, hiding their face behind a mask. Caustic, as a scientist, was always very interested in figuring out the unknown, and so Bloodhound remained a point of constant curiosity. Unfortunately, their skill in battle surpassed his, as they were able to sniff out his traps with ease; each attempt to take them down had ended up with bullets in his back or a knife in his throat.

So... if he’d managed to hit Bloodhound by some chance, then odds were that in addition to finding out how his chemicals worked, he’d be getting to finally figure out that mystery. Not to mention the additional satisfaction he’d get from settling their score, in the most... personal way possible. Now wouldn’t _that_ be marvelous.

With his interest piqued, he leaned around the corner, and from there was able to locate exactly where Mirage was standing guard. Just beneath him, there was a large crevice in the ground that exposed a basement. In front of its two anterior doors stood Mirage... with his back to Caustic.

_No time to waste._ Caustic unhooked one of his traps from his belt, primed it, and tossed it through the gap where it landed with a conspicuous _clunk_. Just as fast as Mirage could turn around, uttering a surprised, “What the hell?”, the trap activated, and it began to spew out the noxious fumes that served as Caustic’s calling card.

Mirage managed to react faster than he expected; even as he began to cough and hack, he pulled out his gun and fired wildly into the gas cloud. When his bullets didn’t connect, he started to stagger over to the adjacent stairs. “L-Lifeline! It’s Caustic!” he croaked, leaning against the wall as he struggled for air. Taking his cue, Caustic jumped down into the narrow gap, ready to take down the opposition. In the name of science, of course.

“Mirage?” Caustic heard Lifeline call from upstairs, and then the thuds of her footsteps as she raced toward the stairwell. Quickly, he pulled his gas grenade from his belt and arced it just-so, watching as it bounced off the wall and rolled into the upper floor. With a hiss, the yellow smog flooded the area, and he heard Lifeline hit the floor as she began to choke on the vapors.

_Too easy_. Once again, no one was a match for the beauty and brutal efficiency of his destructive brand of science. He wasn’t sure why he’d ever thought he needed Bangalore or Wraith.

Satisfied that the opposition had been taken care of, Caustic waded through the mist to the two metal doors. He was preparing to throw them open when suddenly he felt Mirage grab his ankle, trying to ground him as he fumbled for his gun.

It took one simple kick to dislodge him, but since Mirage had decided to be an inconvenience, Caustic advanced on him anyway. Mirage weakly scuttled back, limbs failing him as he breathed in the toxic smog, and it was short work to finish him off with three brutal punches. Mirage’s head smacked against the floor as his body went limp, and Caustic wiped the blood from his gloves onto his apron before turning and pushing open the doors to the interior.

He imagined that he looked rather spectacular, emerging from the gloom of his poisons, but that was nothing, _nothing_ , compared to the sight that awaited him inside.

Sprawled out on the floor before him lay Bloodhound, flushed bright red and gaping at him as he stepped forward. They were partially undressed—and his eyes greedily took in the sight of their exposed, muscled chest—as though he had caught them right in the middle of an attempt to ‘cure’ themself.

“I see you started the experiment without me,” he said with a dark chuckle.

Bloodhound’s jaw snapped shut, and they bared sharp teeth at him in a snarl. “S-stay back.”

“How cute. But a mere show of bravado isn’t enough to stop a dedicated scientist such as I from getting my results,” he said, stalking forward before crouching down in front of the tracker.

Bloodhound shifted away from him as much as they could before their back bumped into the wall. Left with few other options, they struggled to heave their slack limbs to push him away, panting with the effort. It was no more effective than if it had been a stiff breeze. They turned their head to the side, rightfully ashamed.

Curious, Caustic pulled off a glove before lifting a hand to their flushed skin, tracing the curve of their chin, and despite themself, they gasped at the contact. Taking that, and their temperature—which was far out of the normal human range—into account, he was fairly certain that they had reached stage two of the serum.

Their skin was surprisingly smooth.

“Do not touch me,” Bloodhound hissed, straining their neck away from his hand.

“Are you sure about that?” Caustic questioned, with a slight grin. He trailed his hand from Bloodhound’s face to their chest, which heaved with shaky breaths, and as he lingered there, he felt their heart rate spike at the touch. His eyes drank in the sight of their disheveled and flustered state, so far removed from their usual poise and grace.

When Bloodhound didn’t respond, he lowered his hand even further, until it was resting at their waistband. “Don’t,” they insisted, even as their hips shifted slightly beneath his palm.

“I must admit, it’s quite fascinating how the mighty Bloodhound can be lowered to the rest of us mortals with nothing more than an aphrodisiac,” he said, grinning smugly under his mask. “Who knew that the famous, dignified legend was no more than a simple whore?”

Bloodhound reared back as though they had been slapped. “ _Þegiðu_ , dishonor me like that, and I will cut out your tongue and make you swallow it,” they growled.

“Is that what you were thinking of while you were trying to take care of yourself?” Caustic taunted, quite amused at this point. Their threat fell rather flat when he could already feel the faintest hint of wetness through their pants. “Of course, the toxin will dissolve and pass through your liver once your neurons release enough dopamine, but at this point, you have no range of movement to accomplish that. You’ll just sit here, growing more and more desperate, until the ring closes in and slowly kills you.”

“As opposed to the unthinkable,” Bloodhound countered.

Caustic laughed, “I’m not so bad once you get to know me,” as he slowly rubbed his hand over the mound of their crotch. “I think we could make this work for both of us, you know. I get my test results, and you get to cum. I’ll even let you live afterward, I promise.”

“I’d rather die,” Bloodhound gritted out between panting breaths, even as their hips bucked slightly at his touch.

“Of course, I could do that too,” Caustic said, lifting his hand as he shrugged. Bloodhound made a slightly choked sound at the loss of contact, and then immediately turned red with embarrassment. Chuckling, Caustic moved it back between their legs to give a squeeze. “I can also just take what I want. Whether you give me permission or not isn’t relevant at this point. It never was, really.”

Bloodhound winced. “Then why bother asking in the first place, if you intend to act like the scum of the earth anyway?”

Caustic grinned. “Because it’d be a lot more satisfying for me if I got you to beg.”

Their response was to spit at him.

“It’s a shame you’re determined to be difficult about this,” he sighed, wiping it away. “But the round will be over shortly, and I don’t intend to wait for the ring to close in.” He began to lower Bloodhound’s pants below their hips.

“Then leave,” Bloodhound hissed, squirming as much as they could to make Caustic’s job harder. It was really quite pitiful to behold.

He paused only for a moment to make a show of thinking, before saying, “I could, but it would be too rewarding to see you suffer. Revenge is far more intoxicating than any aphrodisiac, wouldn’t you agree?” And with that said, he yanked their trousers down the rest of the way.

Oh. Well, that was interesting.

He must have been sitting there bemusedly for a while, because when Bloodhound finally redirected his attention, it was with a muttered, “Don’t stare, _hálfviti_.”

Caustic blinked before sneering. “Unexpected variables occur all the time in my experiments. You’re far from special.”

Bloodhound looked away at that, seemingly with no more to be said, and Caustic finished removing their pants before taking the opportunity to pull their legs further apart and study what lay between them. Curious, he reached out a finger to trace over the large nub at the crest of their lips, and was immensely satisfied in the halting little moan Bloodhound gave in response.

He lowered his hand further, and rubbed against their folds, the excessive wetness coating the tip of his gloved finger as he probed lightly inside. “I can tell you’re excited,” he quipped, and when Bloodhound continued to remain silent, he slowly slid the finger in deeper, prompting a full-body shudder from them.

He pushed in and out a few times before slipping in a second finger without warning, and he relished the startled moan Bloodhound let out before biting down harshly on their lower lip.

“There’s no point in being shy,” Caustic reasoned as he scissored his fingers inside, pushing in to the last knuckles as he added, “We’re going to be very well acquainted by the end of this experiment, after all.”

“Haah— _farðu í r-rassgat_ ,” they stuttered out through gritted teeth, and Caustic couldn’t care less about figuring out what it meant when he was rewarded for his efforts with a weak but insistent rolling of their hips.

By the time he slipped in the third finger, Bloodhound was panting like they were in the middle of running a marathon, even with his pace measured and deliberate.

“For a man who claims—ah—claims to be in a rush,” Bloodhound hissed, “you are very much taking your time.”

Caustic raised an eyebrow. “You still haven’t given me what I want.” He briefly increased the speed of his fingering and rubbed his now slick thumb over their nub, laughing as Bloodhound jolted like they’d been electrocuted before letting out a low groan. “Once you beg, I’ll let you cum.” Bloodhound turned away from him, and what Caustic could see of their face was bared in a grimace. “Or, I could give you another dose,” he bluffed.

Immediately, Bloodhound’s head whipped back toward him, and their fists clenched where they rested on the ground. “Just imagine, if your arousal is a potent ache now, it will become a much more desperate need with another prick of the needle.” He curled his fingers inside Bloodhound’s heat, and as they whimpered at his touch, he added, “I doubt you’d be able to say no then. So really I’m giving you the chance to maintain some control of this situation. Don’t you want that? You could say yes, and it’d be your choice.”

He watched a bead of sweat curl down Bloodhound’s cheek from beneath their mask and waited for their answer, idly passing over the sensitive node from time to time. With each touch, they let out a quick puff of breath through their teeth. Their fingers would clench, release, and dig weakly into the dirty floor.

Just as he was finally wondering if he’d underestimated their resolve, they tilted their head back, and it made a light clunk against the wall as they rasped, “Get it over with.”

A thrill of excitement ran through Caustic, but he restrained himself; a scientist must have patience to achieve optimal results. “Get it over with...?” he prompted, stilling his hand.

Bloodhound let out an incredulous noise that trailed its way into a defeated sigh. “Get it over with. Please.”

Caustic grinned triumphantly. “It’ll be my pleasure.” Finally, he could get to what he’d been waiting, _aching_ for.

He resumed dipping his fingers in and out of Bloodhound’s opening, giving them a moment to let their guard down before waving a hand in front of their face. No response. And so slowly, tediously, he began to one-handedly take off his yellow apron. It was a bit of a multitasking job, but Bloodhound seemed oblivious to anything other than stimulation they were receiving, if their quiet, continuous hums were any indication.

With the apron set aside, he turned his attention to the zipper of his jumpsuit, discreetly easing it down.

Over the past few Apex Games, he had schemed, fantasized even, about exacting retribution on Bloodhound for the myriad deaths he’d received at their hands. Obviously he could’ve gone for the option of a slow, torturous, messy end; the thought had definitely put a shiver in him. In fact, it had been late at night, as he lay in bed thinking of that scenario, that the idea of experimenting with aphrodisiacs had come to him.

Still, he’d had no idea then who his first test on the battlefield would involve. Hitting Bloodhound with the dart had been an extraordinary stroke of luck.

The sight of Bloodhound beneath him, desperate for any touch, _his_ touch, had made this about more than just simple revenge. There was no ignoring the immense gratification, beyond simple pride, that the thought of ‘getting even’ with Bloodhound in this way brought him.

So, considering all of that, the impatience with which he suddenly grabbed and lifted Bloodhound’s legs, and spread them to their sides before shifting forward and thrusting into them was to be expected, really.

The horrified cry Bloodhound let out at the sudden intrusion, coupled with the sensation of sinking quickly into their wet warmth, was already almost enough to push him over the edge. But he didn’t go through all of this work just to lose it immediately. No, that wouldn’t do at all.

Bloodhound was stock-still beneath him, save for a slight shaking in their legs and the rapid rising and falling of their chest. Their fingers were clawed into the dirty ground, and their head was angled to the side. When he gave an experimental thrust, he felt Bloodhound shudder, but that was it.

“There’s no point in fighting against it,” Caustic said, almost breathlessly. “I haven’t tested it thoroughly enough to know if it’d fix the paralysis in that case.”

Bloodhound spared a glance at him, and as they did, he saw their teeth clenched tightly over their bottom lip, a slight trail of blood dripping down to the point of their chin. Caustic felt an almost primal urge to lean in and taste it, but... no. He was a paragon of rationality, not an animal. He chose to instead satisfy himself with a few more thrusts, at a quicker pace this time.

He must’ve hit an erogenous zone, because Bloodhound suddenly tipped their head back again, and let out a low, strained groan. Their walls fluttered and clenched around him, and Caustic allowed himself a short, heated moan, reveling in the sensations of slick tightness and the frantic pulsing of their heartbeat, and he pushed one of their thighs farther to the side to get a better angle to pound into them.

As they twitched beneath him, he leaned in and supported himself with a palm against the wall by their head. When he was close enough to see himself in their lenses, they winced, and finally spoke. “When this is over, _andskotinn_ ,” they hissed with a venomous voice, “you will wish—ah—you will wish you had never been born.”

Caustic let out a low, dark laugh. “You may act like you resent this, but I have enough faith in my chemistry to know that you’re actually enjoying yourself.” He pushed in to the hilt, and as they let out a quiet whine, he added, “You’re just too stubborn to admit it.”

“You’re cruel to think anyone could enjoy this.”

“Perhaps,” Caustic acquiesced, “But suppose, for a moment, that what matters more is that _I_ am very much enjoying this.”

Caustic began to move faster. He could feel that he was approaching his limit, and he was certain that it would be more enjoyable if he could get Bloodhound to topple over the threshold before he did.

His movements shook the hunter below him, and as they panted desperately, he reached just the right pace and position to get what he wanted. They went still beneath him for a moment before finally, finally, they let out a long, desolate moan, and began to tremble through their release. He thrusted into them through it until the end, able to go faster with the incredible amount of slick, and then he kept going, even as they let out a whimper of pain.

“W-what... what did you do? My body, it—it hurts,” they groaned, voice weak as they gingerly struggled to shift beneath him.

“Just a side effect,” Caustic grunted through his growing haze of pleasure, “A sort of parting gift, if you want to think of it that way.” He slammed into them, and feeling them quake beneath him was nearly enough. “It’ll all be over soon.”

He could feel the pleasure radiating through him, lighting up his senses. He had finally done it, finally gotten revenge on, and completely ruined, the enigmatic Bloodhound. He was so close, he could almost taste it—

And then he heard Bloodhound let out a grunt of effort beneath him, followed immediately by a sharp, shooting _ache_ in his side.

He slowed to a stop, leaned back, and looked down at his chest, where Bloodhound’s hunting knife was buried into his side. A trickle of blood oozed down the blade.

And then with another wheezing huff, Bloodhound pulled out the dagger before stabbing it squarely into his chest.

And then stabbed again.

When Caustic fell onto his back, burning through with pain, they shakily crawled on top of him, holding the blade to his throat.

“ _Mannfjandi_ ,” they spat, resolute above him in spite of their pain. “You will rot for eternity in the guts of _Níðhǫggr_ , and as a tool of the gods, I will send you to him!”

Despite the slow creeping of blood into his throat, Caustic laughed, the sound a morbid gurgle. “If the ‘gods’ cared, don’t you think... they would’ve stopped me?”

Bloodhound faltered for a moment above him.

He grinned up at them like a skull. “Maybe they thought you deserved it.”

They were still for barely a moment more before their jaw clenched in absolute fury and disgust, and they pushed off of him back onto their haunches, where they reached their hand down to grasp his shaft in a bitingly tight grip, and he was confused but hopeful for the brief moment in between that and when the cold steel of their knife bit into sensitive flesh.

Caustic yelled, agony coursing through his every nerve. The pain was like nothing he’d ever felt before. He fought to rise from his position on the ground, to stop them, but the stab wounds in his chest were fast robbing him of his strength. He could do nothing but lay there and howl and groan until their blade cut all the way through.

_Another unexpected variable,_ he thought deliriously, and he managed to choke out a sour laugh through the pain.

He was teetering on the edge of oblivion, and one of the last sensations he felt was Bloodhound prying his mask off, opening his clenched teeth, and shoving the soft, bleeding flesh inside his mouth until he began to choke. As his vision faded, he heard them hiss, “Feel the pain you have inflicted on me, tenfold, from now until the end of time. _Hlandbrenndu_.”

And then the world went dark.

**Author's Note:**

> "what a boner kill as they say" - My beta reader's review of the ending
> 
> Bloodhound never really struck me as a wilting lily; in an unfortunate situation, they'd bide their time and wait until the moment was right to strike and get retribution. And besides, they're my favorite character, so I _had_ to let them be victorious in the end.


End file.
